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http: create header field names as internalized strings #64277

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http: create header field names as internalized strings #64277

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f1a205d
http: create header field names as internalized strings
araujogui Jul 4, 2026
fff2fbc
http: only internalize short header field names
araujogui Jul 4, 2026
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4 changes: 3 additions & 1 deletion src/node_http_common.h
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,8 @@ class Environment;
#define DEFAULT_MAX_HEADER_LIST_PAIRS 128u
#define DEFAULT_MAX_HEADER_LENGTH 8192

constexpr size_t kMaxInternalizedHeaderNameLength = 64;

#define HTTP_SPECIAL_HEADERS(V) \
V(STATUS, ":status") \
V(METHOD, ":method") \
Expand Down Expand Up @@ -432,7 +434,7 @@ class NgRcBufPointer : public MemoryRetainer {
return v8::String::Empty(env->isolate());
}

if (ptr.IsInternalizable() && len < 64) {
if (ptr.IsInternalizable() && len < kMaxInternalizedHeaderNameLength) {
v8::MaybeLocal<v8::String> ret = GetInternalizedString(env, ptr);
ptr.reset();
return ret;
Expand Down
17 changes: 16 additions & 1 deletion src/node_http_parser.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@
#include "llhttp.h"
#include "memory_tracker-inl.h"
#include "node_external_reference.h"
#include "node_http_common.h"
#include "stream_base-inl.h"
#include "v8.h"

Expand Down Expand Up @@ -65,6 +66,7 @@ using v8::Isolate;
using v8::Local;
using v8::LocalVector;
using v8::MaybeLocal;
using v8::NewStringType;
using v8::Number;
using v8::Object;
using v8::ObjectTemplate;
Expand Down Expand Up @@ -233,6 +235,18 @@ struct StringPtr {
return String::Empty(env->isolate());
}

Local<String> ToInternalizedString(Environment* env) const {
// Only internalize short names to avoid pressuring the string table.
if (size_ != 0 && size_ < kMaxInternalizedHeaderNameLength) {
return String::NewFromOneByte(env->isolate(),
reinterpret_cast<const uint8_t*>(str_),
NewStringType::kInternalized,
size_)

@jasnell jasnell Jul 8, 2026

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hmm.. I'm not convinced this is a good idea.

While it certainly helps legitimate cases, there's a risk here.

A malicious sender could leverage this into a memory leak or cause significant additional GC pressure pretty easily by sending a large number of intentionally different header values at a high rate. Internalized strings do get cleaned up during a major GC. The current existing non-internalized strings can be cleaned up in a minor GC.

We really ought to be internalizing only known header names.

@araujogui araujogui Jul 8, 2026

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You're right, should I apply the same fix on the HTTP/2 path?

node/src/node_http_common-inl.h

Line 126 in 8e1ab55

name_.reset(name, true); // Internalizable

.ToLocalChecked();
}
return ToString(env);
}

// Strip trailing OWS (SPC or HTAB) from string.
Local<String> ToTrimmedString(Environment* env) {
while (size_ > 0 && IsOWS(str_[size_ - 1])) {
Expand Down Expand Up @@ -940,7 +954,8 @@ class Parser : public AsyncWrap, public StreamListener {
Local<Value> headers_v[kMaxHeaderFieldsCount * 2];

for (size_t i = 0; i < num_values_; ++i) {
headers_v[i * 2] = fields_[i].ToString(env());
// Field names repeat across requests, so internalize them.
headers_v[i * 2] = fields_[i].ToInternalizedString(env());
headers_v[i * 2 + 1] = values_[i].ToTrimmedString(env());
}

Expand Down
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